Coal or ore washing



8" 7, 1952 J. E. CHICK EI'AL 3,048,273

COAL OR ORE WASHING Filed July 15, 1959 4 Sheets-Sheet 1 Invezators 1952 J. E. CHICK ETAL 3,048,273

COAL OR ORE WASHING Filed July 13. 1959 4 Sheets-Sheet 2 IN V EN TORS 1952 J. E. CHICK EIAL 3,048,273

COAL OR ORE WASHING Filed July 15, 1959 4 Sheets-Sheet 3 IN V EN TORS 1952 J. E. CHICK EIAL 3,048,273

COAL OR ORE WASHING Filed July 13, 1959 4 Sheets-Sheet 4 IN V EN TORS United rates Our present invention relates to a method and an apparatus for separating ores, particularly coal, in a single fractionation, into a fraction of least density, for example coal, a fraction of intermediate density, for example mixed coal and rock, and a fraction of greatest density, for example slate or rock.

The invention is particularly useful in separating coal as mined from slate or other rock associated with the coal. The lightest fraction of such a mixture is substantially coal with little or no rock or gangue. The intermediate fraction is made up of particles of coal, and rock from which the coal may be recovered by further fragrnentation and separation. The heaviest fraction is composed of rock particles with little or no coal. The density of all of these fractions is somewhat greater than that of water. However, an aqueous liquid of a density sufficient to float the lightest fraction and of a density to float the intermediate fraction may be formed by suspending in water a suitable heavy solid such as magnetic iron oxide in such fine particles that separation of the particles is negligible in use. Thus by using a medium having a density greater than that of the lightest fraction but less than that of the intermediate fraction the lightest fraction will float to the surface while the intermediate and heaviest fractions will sink, and by using a medium of a density greater than that of the intermediate fraction and less than that of the heaviest fraction the intermediate fraction will float and the heaviest fraction will sink. Thus a mixture of coal and rock as it comes from the mine may be fractionated into a light fraction, known as floats, an intermediate fraction, known as middlings, and a heavy fraction, known as sinks.

To avoid unnecessary handling of the material, it is desirable to make the fractionation in a single step and in a single apparatus. It has been proposed to use for this purpose an aqueous medium that increases in density gradually or in several increments from the surface downwardly, withdrawing the floats from the upper surface, the middlings from an intermediate zone and the sinks from the bottom. This system does not, however, produce satis factory results. Better results might have been possible by providing a thin interface between an upper, lighter, medium of uniform densityand an under medium of greater density so that upon supplying a mixture to the media the floats would rise to the surface of the lighter medium, the middlings to the interface, from whence they could be withdrawn separately, while the sinks would sink to the bottom.

Heretofore attempts to maintain a clearly defined horizontal interface between an upper medium of lighter density and a lower medium of heavier density and to withdraw the separated fractions from the interface without mechanical means have not proven successful. Such mechanical means prejudice the accurate separation of the fractions because they interfere with the clear separation of the components, particularly of the finer particles.

Our invention provides means whereby a body of lesser density of aqueous medium may be maintained on a body of aqueous medium of greater density with a common horizontal interface and in which the fraction of least density is carried in the upper surface of the medium of lighter density to one side of the medium, the middlings atent i 3,048,273 Patented Aug. 7, 1962 are carried by the movement ofthe medium of lower density at the interface to a station to be removed and the sinks are carried from the bottom of the medium of higher density. The area of the interface is reduced by reducing the dimensions of the area, thereby reducing the opportunity for destruction of the interface. Mixing of the lighter and denser media is also minimized by floating the middlings out of the interface by the transverse movement of the denser medium thus avoiding mechanical means and the agitation occasioned thereby. The middlings are floated into a separate compartment from which they are carried away by a mechanical means. The level of the interface is controlled by an adjustable overflow weir.

In a specific embodiment of the invention the sinks and middlings are conveyed from the separating vessel containing the separating media by a wheel having two concentric series of pockets, one positioned to rotate to bring successive pockets into the bottom of the separating vessel and out to a position to release the sinks at one station. The other series of pockets rotates into the separate compartment to engage the middlings and to carry them to a different station. The plane and the axis of the wheel are inclined to the horizontal at a suit able angle such as 45 to the Vertical and the wheel moves in an inclined cylindrical container or box the lower part of which forms the lower part of the separating vessel and the upper part of which contains separate openings or chutes for the discharge of the sinks and middlings.

The invention is illustrated, by way of example, in the accompanying drawings in which;

FIG. 1 is a perspective view of apparatus according to the invention,

FIG. 2 is a vertical section of the apparatusin a plane V through the axis of the wheel,

FIG. 3 is a section on the line 3--3 of FIG. 2, parts being broken away to show details of underlying elements,

FIG. 4 is a plan view of the separating vessel containing the liquid media, and i FIG. 5 is a vertical section of the separating vessel taken on line 5-5 of FIG. 4.

The separating vessel 1 comprises a hollow, opentopped, vessel bounded by the generally-sloping walls, 2, 3, 4, 5, 6 and 7.

Of these walls, the walls 2 and 3 are, respectively, the rear and peripheral walls of a box in which the wheel 8 is adapted to rotate; the wall 3 being cylindrical and completely surrounding the periphery of the wheel and the wall 2 completely coven'ng its underside. The outside periphery of the wall 4 is semi-circular in shape and extends around the lower half of the periphery of the wheel 8 and terminates on each side at the horizontal diameter thereof. It is connected to the upper edge of the wall 3. Its inner edge is semi-circular in shape and lies above a cylindrical wall 9 which forms the division between an inner and an outer series of annular concentric compartrnents which form the radially-outer portion of the wheel Sand will be described hereunder. V

The walls 5 and 7 are substantially identical but are arranged in opposite sense and, referring to wall 7, each comprises a lower triangular vertical portion 7a and an intermediate portion 7b which slopes outwards away from the opposite wall 5 and is connected at its lower edge to the hypotenuse of the triangular wall 7a. A rectangular portion 70 is connected to the upper edge of the sloping portion 711 and lies parallel with the plane of the portion 7a. The portion equivalent to the portion 70 isomitted from the wall 5. The lower edges of the wall portions 5a and 7a are connected to the surface of the wall 4 in spaced relation on each side of the lower vertical radius a 3 of the wheel 8, and extend outwardly at right-angles to the wall 4.

The lower outer edge of each wall portion 5a and 7a is connected to opposite sides of the lower portion 6a of the wall 6. The 'wall 6 is in three portions, of which the vertical portion 6c lies in a plane normal to the planes of the. wall portions 7c and 5 and is connected at one end to the Wall portion 7c. The portion 6b of the wall 6 slopes inwardly towards the wheel. 8 at the same angle as the wall portion 7b and is followed by the wall portion 6a which slopes at a lesser angle and has its lower edge secured to the walls 4, 5 and 7. The rectangular space in the wall 4 defined by the junction of the walls 5, 6 and 7 therewith is cut away to form an aperture 10 in the wall 4 to permit the flow of fluent materials from the lower portion of the vessel 1 into the space bounded by the walls 2, 3 and 4. The upper edges of the walls 6 and 7 lie below the upper edges of the wall 4, and the upper edge of the wall 5 lies below the upper edges of the walls 6 and 7 for reasons which will later become apparent.

A further vertical wall 11 extends vertically upwards from the inner end of the lower edge of the wall portion 70, and, from a position where it lies adjacent the upper surface of the wheel, is continued upwards into horizontal alignment with the upper edges of the wall 4. It is connected to the wall 4 at each end by a triangular gusset 12. The opposite ends of the wall 11 extend outwards at each side of the walls 5 and 7 and are of a length equal to the diameter of the cylindrical wall 9. At the lower-edge of the wall 11 a sloping portion 11a is secured at its opposite ends to the sloping portion 712 and equivalent portion of the wall 5, extends downwards for substantially half the depth of the wall portion 7b toward parallelism with the walls 2 and 4 and thus with the plane of the wheel 8. The wall 11 and extension 11a divide the separating vessel -1 into a compartment 1a which receives the material to be separated into fractions and a compartment 1b communicating with the compartment 1a through a passage 1112 between the lower edge of the wall 11a and'the opening 10.

The rear wall 2, circular in form, is secured to the underside of a non-rotatable boss 13 which has a substantially circular periphery. For a short distance on each side of the vertically-upper radius of the boss a rectangular recess 14, FIGS. 1, 2 and 3, is cut in its periphery to coincide with a hole 15 cut in the rear wall 2. The wheel 8, in operation, is rotated in a counter-clockwise direction as seen in the drawing, and the periphery of the boss 13 is formed eccentrically for a short distance on the trailing side of the recess 14, as at 16, FIGS. 1 and 3, so that the edge 17 of the recess 14 is of lesser radialdepth than the opposite edge thereof. The eccentric portion 16 gradually merges into the concentric periphery of the boss.

The Wheel 8 is rotated by a suitable prime mover (not shown) through a driving spindle 18 rotatable in bearings (not shown) in the boss 13, and is supported on the spindle 18 by axially spaced plates 19, 20 suitably secured to the spindle. A plurality of arms 21 extend radially outwards from the plates 19, 20 and form a spider to which are secured the two concentric annuli of compartments referred to hereabove.

'Iheradially-inner annulus compartments comprises an annular perforated metal trough member 22, having a tapered cross section and the base of which lies at an angle to the plane of the wheel. The radially-outer limb of the trough member comprises the wall 9, previously referred to, which, due to the angular aspect of the base relative to the plane of the wheel, is substantially cylindrical relative to the wheel. The wall lies normal to the plane of the rear wall 2 from which its inner edge is spaced by a distance equal to substantially half of the vertical depth of the peripheral wall 3. The upper edge of the cylindrical wall 9 lies in the same plane as the upper edge of the wall 3 and is thus in substantial alignment with the inner peripheral edge of the annular front wall 4. The wall 9 lies substantially midway between, and concentric with, the periphery of the plate 19 and the wall 3.

The radially inner limb 23 of the annular trough member 22 lies substantially parallel to, and adjacent, the rear wall 2, with its inner peripheral edge lying closely adjacent the periphery of the boss 13. This inner edge is supported and stiffened by an annular angle member 24 secured to the underside of the limb 23. The intermediate limb, or web, 25 of the trough member 22 is disposed at an angle to the plane of the rear wall 2 and joins together the limbs 9 and 23.

Secured to the rear wall 2 on a circumference which coincides with the circumference of the annular limb 9. of the trough member 22 is a cylindrical shroud 26 which extends upwardly, normal to the plane of the rear Wall 2, to a position where its upper edge lies just clear of the underside of the trough member 22 at the point of junction between the limb 9 and the web 25 thereof. The shroud 26 is cylindrical except for a recessed portion 27 which is directed radially inwardly towards the recess 14 in the boss 13 and is of substantially the same circumferential width, and is disposed on the same radii, as the recess 14. The recessed portion 27 extends radially in wards to a position where its wall lies substantially below the junction of the wall 23 with the web 25 and the upper edge of the shroud 26 is tapered downwards towards the rear plate 2, as at 28, so that at this point the walls 29 of the recessed portion 27 lie closely adjacent the underside of the web 25 which, as has previously been described, lies at an angle to the plane of the rear wall 2. An aperture 30 is formed in the rear plate 2, within the area defined by the walls 29 of the shroud, and this aperture is extended slightly radially outwardly of the periphery of the cylindrical portion of the shroud 26.

The annular trough 22 is divided into a plurality of radial compartments by perpendicular perforated walls 31, the radially-inner edges of which lie closely adjacent the boss 13 and the outer edges of which extend for a short distance up the cylindrical wall 9. At the upper edge of each perpendicular wall 31 is secured a sloping perforated wall 32 which is co-extensive with the wall 31 in a.radially-inward direction and is secured to the cylindrical wall 9 at its other end. The walls 32 are angularly directed in the direction of rotation of the wheel 8 and thus act as weirs to the walls 31 to increase the amount of material that can be lifted in the compartments as the wheel 8 is rotated.

The annular angle member or ring 24 is supported by the plates 19 and 20 through supporting members 33, FIGS. 1 and 2, passed perpendicularly therethrough and the inner ends of the walls 31 are also supported by the members 33.

A further annulus 34 of right-angled cross-section is supported by the members 21 radially outwards of the annular trough 22. The annulus 34 is formed of perforated metal and comprises a cylindrical side wall 35, which lies slightly clear of the cylindrical wall 3, and an annular bottom wall 36 which is disposed parallel with the rear wall 2 and lies slightly clear thereof. The inner periphery of the bottom wall 36 lies closely adjacent the outer periphery of the shroud 26. The bottom wall 36 also lies in substantially the same plane as the wall 23 of the annular trough 22.

The annulus 34 is divided into a plurality of radial compartments by a plurality of perpendicular perforated radial Walls 37 secured to the wall 35 and the bottom wall 36. The inner edges of the walls 37 lie closely adjacent the outer peripheryof the shroud 26 and extend slightly above its upper edge. Upon rotation of the wheel 8, the two annuli 22 and 34 are rotated around the boss 13 with the inner edges of the walls 23 and 31 moving closely therearound and the inner edges of the walls 36 and 37 moving closely around the shroud 26. The web 25 of the inner annulus 22 passes closely over the upper edges of the walls 29 of therecess 27 in the shroud 26.

As the wheel rotates, each of the compartments in the annuli 2'2 and 34 in turn comes opposite the recesses 14 and 27, respectively, so that anything contained in either of the compartments opposite one of the recesses is free to pass out of the compartment and to fall through the aperture or 30 in the rear wall 2. Suitable chutes or the like (not shown) will normally be provided to maintain the separation of the materials falling through the apertures.

The compartments in the annulus 22 will pick up the middles product and those in the annulus 34' will pick up the sinks product, as later to be described.

Low density liquid medium of the required specific gravity is introduced into the separating vessel 1 from stock tanks (not shown) through inlets 38, FIGS. 1, 4

and 5, near the top of the vessel and liquid medium of a higher specific gravity is introduced into the bottom of the vessel 1 from other stock tanks through the inlets 39, FIGS. 1, 2 and 5, all in such a manner that an interface is formed between the two mediums of different density; the interface occurring below the level of the junction of the wall portions 711 and 7b, i.e. below the level of the lower edge of the wall 11a and at about the level of the upper edges of the inlets 39 or thereabove.

Means are provided to permit a constant flow of high density medium through the lower portion of the separating vessel 1 so that the interface between the low and high density mediums is maintained as a clear-cut barrier and for this purpose one or more outletconduits 44 FIGS. 1 and2 from the vessel 1 through the rear plate 2 are provided, to provide an overflow passage or passages therefrom into a compartmented header tank 41.

The header tank 41 comprises two compartments 42 and 43 vwhich are separated by a transverse Wall, to the upper end of which is fitted a vertically-adjustable weir 44, the upper edge of which may be suitably raised or lowered to provide for the continuous overflow of all the dense medium not carried away in the sinks and middles products, together with a small amount of the lowdensity medium adjacent the interface. The level of the interface is determined by the level of the weir 4,4, the flow of dense medium being of such volume and strength that the interface zone is kept continuously free from dilution by any low density medium carried down by the middles and sinks products.

From the header tank 41 the overflowing medium is carried by the conduit 45 to a suitable stock tank, filter, classifier or medium recovery system as may be required and as known in the art.

In the operation of the apparatus, high density liquid medium is fed into the bottom of the vessel 1 through the inlets 39 and low density medium is fed into the vessel, at right angles to the high density feed, through the inlets 38 until the interface is obtained and overflow in to the header tank 41 commences.

In the present instance, the wheel 8 is rotated in a counterclockwise direction, although the direction of rotation is not an essential feature of the invention and the wheel may be adapted for rotation in a clockwise direction merely by reversing the slope of the weir plates 32 and the position of the portion 16 of the boss 13.

Coal is then fed into the outer portion of the vessel 1 from a suitable conveyor (not shown) on the same side of the vessel as the inlets 38, and the floats product, although some plummeting may occur as the coal enters the low density medium, floats to the surface and is carried across the vessel over the top of the wall 5 (from which the portion equivalent to the wall portion 70 is omitted) and passes to screens and conveyors by which it is carried away in the normal manner known in the art.

The sinks and middles products, being of higher specific gravity than the low density medium, sink therethrough until they reach the interface between the low and high density mediums. .The high density medium is of a higher specific gravity than that of the middles product,

which thus floats at the interface and, as the high density medium is flowing towards the wheel 8; the floating midmiddles product in the compartments is carried around until the compartment comes opposite to the recess 14 in the boss .13, when the middles product falls out of the compartment through the aperture 15 into a suitable chute, hopper or conveyor. The eccentric portion 16 of the boss 13 is provided to prevent jamming of the wheel by any product which has not fallen clear of the compartment and has a camming action thereon which gradually pushes any remaining product back into the compartment before the adjacent end of the wall 32 again comes close to the concentric periphery of the boss 13.

The remaining portion of the product which has sunk in the low density medium and has failed to float in the high density medium sinks toward the bottom of the vessel and is carried by the flow from the inlets 3-9, assisted by the taper of the wall portion 6a, into the compartments of the outer annulus 34 and is carried around by the wheel until the respective'compartments come opposite the aperture 36 and recess 27 in the shroud 26, when the sinks product falls through the aperture 30 into a suitable chute, hopper or the like.

Some of the liquid medium in the respective products carried by the wheel drains therefrom as the wheel rotates, but, as this falls into the vessel to the rear of the wall 11 it doesnot return to the separation portion of the yessel but is carried through the conduit 40 to the header tank 41.

What we claim is: 1. A method for separating solids into fractions of greateshintermediate and least densities which comprises introducing said solids into a liquid medium having a lower body of a density between the density of the fractions of greatest and of intermediate densities and. an upper body of a density between the density of the fractions of intermediate and least densities superposed on said lower body and having a common horizontal interface of separation; flowing liquid at the upper surface of said upper body from one side thereof to the opposite side to float said fraction of least density to said opposite side, flowing liquid medium of said lower body from one side thereof to the opposite side thereof at said interface to float said fraction of intermediate density to said opposite side, and separately removing said floated fractions of least and intermediate densities from said surface and from said interface and said fraction of greatest density from the bottom of said lower body.

2. The method of claim 1 in which said lower body extends sidewise of said interface and in which said fraction of intermediate density is floated to said sidewise extending portion of said lower body.

3. Apparatus for separating solids into a fraction of greatest density, a fraction of intermediate density and a fraction of least density which comprises a container having a partition extending downwardly and terminating in a lower edge above the bottom of said container to divide the upper part of the container into a solids separating compartment and a solids receiving compartment, means to supply a first liquid medium of a density be tween that of the fractions of greatest and intermediate densities to the side of said container opposite said partition and below the edge of said partition to provide a compartment transverse to said partition above the lower a ment being adapted to receive solids supplied thereto to be fractionated, and means to pick up and remove separately the intermediate fraction from the solids receiving compartment and the fraction of greatest density from the bottom of said container.

4. The apparatus of claim 3 in which said partition and the sides of said container are inclined downwardly and inwardly to provide an interface between said upper and lower bodies of liquid medium in said solids separating compartment of lesser area than the area of the surface of said upper body of liquid medium.

5. The apparatus of claim 4 in which both dimensions of the area of said interface within said solids separating compartment are less than corresponding dimensions of the surface of the upper body of liquid medium.

6. The apparatus of claim 3 in which said means to pick up and remove separately the intermediate fraction and the fraction of greatest density comprises a wheel rotably mounted to said container and having one circular series of pockets positioned to receive solids floated into said solids receiving compartment and a second series of pockets positioned to receive solids sinking to the bottom of said solids separating compartment.

7. The apparatus of claim 6 having a circular box forming part of the lower part of said container and extending upwardly therefrom and in which said wheel is mounted in and concentric with said box, said box having separate discharge openings above the axis of said wheel and above the upper overflow of said container to receive solids separately from each series of pockets.

8. The apparatus of claim 7 in which said wheel has an outer circular wall and an inner circular wall concentric with and spaced from said outer wall, said walls being concentriewith the axis of rotation of the wheel, and partitions extending radially inwardly at spaced intervals from said circumferential walls.

9. The apparatus of claim 8 in which the bottoms of said inner series of pockets are inclined downwardly from said inner cylindrical wall of said wheel.

10. The apparatus of claim 8 in which the walls of said pockets are foraminous.

11. The apparatus of claim 8 in which the plane of said wheel is inclined at an angle of 45 to the horizontal.

12. The apparatus of claim 7 in which the pockets of each series are open inwardly toward the center of said Wheel and in which said box has a circular partition closing the open sides of the outer series of pockets and a circular partition closing the open sides of the inner series of pockets and in which each said circular partition has an opening to its respective discharge opening in said box.

13. The apparatus of claim 3 having a vertically adjustable weir connected to said overflow from said solids receiving compartment to adjust the height of the interface between the liquid media in said solids receiving compartment.

References Cited in the file of this patent UNITED STATES PATENTS 2,496,703 Ekbom Feb. 7, 1950 2,744,627 Erk May 8, 1956 2,798,606 Dru July 9, 1957 2,889,043 Dru June 2, 1959 2,899,057 Menzies Aug. 11', 1959 2,899,058 Tromp Aug. 11, 1959 FOREIGN PATENTS 68,815 France Feb. 3, 1958 (6th Addition to 993,355) r 549,222 Canada Nov. 26, 1957 

